Visualization systems and methods for optimized optical coherence tomography

ABSTRACT

The present disclosure provides a visualization system for performing optimized optical coherence tomography (OCT) by determining the absolute distance between the OCT source and a sample. The present disclosure also provides a method for optimizing OCT, which includes determining an absolute distance between the OCT source and a sample using data relating to the focal length or position of an autofocus imager lens.

TECHNICAL FIELD

The disclosure relates to optical coherence tomography (OCT), and morespecifically, to visualization systems and methods for optimized OCTscanning.

BACKGROUND

Eye surgery, or ophthalmic surgery, saves and improves the vision oftens of thousands of patients every year. However, given the sensitivityof vision to even small changes in the eye and the minute and delicatenature of many eye structures, ophthalmic surgery is difficult toperform and the reduction of even minor or uncommon surgical errors ormodest improvements in accuracy of surgical techniques can make anenormous difference in the patient's vision after the surgery.

Ophthalmic surgery is performed on the eye and accessory visualstructures. During ophthalmic surgery, a patient is placed on a support,facing upward. The support may a couch or a bed and may be positionedunder a surgical microscope. An eye speculum is inserted to keep the eyeexposed. Surgeons often use the surgical microscope to view thepatient's eye, and surgical instruments may be introduced to perform anyof a variety of different procedures. The surgical microscope providesimaging and optionally illumination of parts of the eye during theprocedure.

In addition to simply allowing a close-up view of the eye, a surgicalmicroscope may be equipped with an OCT system to provide additionalinformation about internal structures of the eye that cannot effectivelybe seen using only the surgical microscope. OCT systems may be opticallyor electro-mechanically integrated into the surgical microscope.

OCT is an interferometric analysis technique for structural examinationof a sample that is at least partially reflective to light, for example,a biological tissue. OCT can also be used for functional examination ofa sample, such as the motion and velocity of the sample or blood flow ina tissue. OCT systems may be used to determine distance and depthprofiles and other information based on interference patterns created bythe interaction between a reflected beam from a reference mirror and areflected beam from a sample.

In an OCT system, a single OCT source beam is split into two componentbeams, a sample beam that is propagated to and at least partiallyreflected by a sample, and a reference beam that is propagated to andreflected by a reference mirror. Each beam is typically reflected backto the beam splitter and combined, although certain OCT systems may notrequire each reflected beam to return to the beam splitter to becombined. When the reflected sample beam and reflected reference beamare combined, an interference pattern is generated, which may be used tomeasure distances and depth profiles of the sample and other informationand to image internal target structures that the sample beam passedthrough. In ophthalmic surgery, an OCT system may be used, for example,to provide cross sectional views of the retina in high resolution.

SUMMARY

The present disclosure provides a visualization system that includes anOCT system with an OCT source that is operable to generate an OCT sourcebeam, an OCT beam splitter, and an OCT detector. The OCT beam splitteris operable to split the OCT source beam into a sample beam that travelsalong a sample arm until it is reflected by a sample to form a reflectedsample beam, and a reference beam that travels along a reference armuntil it is reflected by a reference mirror in the OCT system to form areflected reference beam, and operable to combine the reflected samplebeam and the reflected reference beam to form a reflected OCT beam. TheOCT detector is operable to receive the reflected OCT beam and operableto detect an interference pattern of the reflected OCT beam. Thevisualization system also includes a surgical microscope, a dichroicmirror operable to allow non-OCT light to substantially pass through andoperable to reflect the sample beam, and a visualization beam splitteroperable to direct non-OCT light into both the surgical microscope andan autofocus imager. The autofocus imager is operable to receive non-OCTlight reflected by the sample that has passed through the dichroicmirror and has been directed by the visualization beam splitter to theautofocus imager. The autofocus imager is operable to use the non-OCTlight reflected by the sample to optimize the focus of the autofocusimager on the sample by adjusting an autofocus imager lens, and isoperable to generate data relating to a position or a focal length ofthe autofocus imager lens. The visualization system further includes aprocessor operable to determine a distance between the dichroic mirrorand the sample using the data relating to the position or the focallength of the autofocus imager lens, determine an absolute distancebetween the OCT source and the sample using the distance between thedichroic mirror and the sample, determine a length of the sample armusing the absolute distance between the OCT source and the sample,generate a control signal operable to optimize the OCT system byadjusting the length of the reference arm or the focus of the samplearm, and transmit the control signal to the OCT system.

In additional embodiments, which may be combined with one another unlessclearly exclusive: the autofocus imager lens is a power adjustable lens,and a focal length of the power adjustable lens is adjusted; theautofocus imager lens is a position adjustable lens, and a position ofthe position adjustable lens is adjusted; the processor is operable tocalculate the length of the sample arm, using the absolute distancebetween the OCT source and the sample, generate and transmit the controlsignal in real time; the processor is operable to determine the absolutedistance between the OCT source and the sample by reference tolens-distance reference data; and the lens-distance reference dataincludes data corresponding to the distance between the OCT source andthe sample at different focal lengths or positions of the autofocusimager lens.

The present disclosure further provides a visualization system thatincludes an OCT system with an OCT source that is operable to generatean OCT source beam, an OCT beam splitter, and an OCT detector. The OCTbeam splitter is operable to split the OCT source beam into a samplebeam that travels along a sample arm until it is reflected by a sampleto form a reflected sample beam, and a reference beam that travels alonga reference arm until it is reflected by a reference mirror in the OCTsystem to form a reflected reference beam, and operable to combine thereflected sample beam and the reflected reference beam to form areflected OCT beam. The OCT detector is operable to receive thereflected OCT beam and operable to detect an interference pattern of thereflected OCT beam. The visualization system also includes a surgicalmicroscope, a dichroic mirror operable to allow non-OCT light tosubstantially pass through and operable to reflect the sample beam, anda visualization beam splitter operable to direct non-OCT light into boththe surgical microscope and an autofocus imager. The autofocus imager isoperable to receive non-OCT light reflected by the sample that haspassed through the dichroic mirror and has been directed by thevisualization beam splitter to the autofocus imager. The autofocusimager is operable to use the non-OCT light reflected by the sample tooptimize the focus of the autofocus imager on the sample by adjusting anautofocus imager lens, and is operable to generate data relating to aposition or a focal length of the autofocus imager lens.

The visualization system further includes a processor operable todetermine a change in distance between the dichroic mirror and thesample using the data relating to the position or the focal length ofthe autofocus imager lens, determine a change in the length of thesample arm using the change in distance between the dichroic mirror andthe sample, generate a control signal operable to optimize the OCTsystem by adjusting the length of the reference arm or the focus of thesample arm, and transmit the control signal to the OCT system.

In additional embodiments, which may be combined with one another unlessclearly exclusive: the autofocus imager lens is a power adjustable lens,and a focal length of the power adjustable lens is adjusted; theautofocus imager lens is a position adjustable lens, and a position ofthe position adjustable lens is adjusted; and the processor is operableto determine the change in the length of the sample arm using the changein distance between the dichroic mirror and the sample, generate andtransmit the control signal in real time.

The disclosure also provides a method for optimizing optical coherencetomography (OCT) that includes receiving, at an autofocus imager,non-OCT light reflected by a sample, the non-OCT light having passedthrough a dichroic mirror and having been directed by a visualizationbeam splitter to the autofocus imager, using the non-OCT light reflectedby the sample, at the autofocus imager, to optimize the focus of theautofocus imager on the sample by adjusting an autofocus imager lens,generating data, by the autofocus imager, relating to a position or afocal length of the autofocus imager lens, determining a distancebetween the dichroic mirror and the sample using the data relating tothe position or the focal length of the autofocus imager lens,determining an absolute distance between the OCT source and the sampleusing the distance between the dichroic mirror and the sample,determining a length of the sample arm using the absolute distancebetween the OCT source and the sample, generating a control signal, thecontrol signal operable to optimize the OCT system by adjusting thelength of the reference arm or the focus of the sample arm, andtransmitting the control signal to the OCT system.

In additional embodiments, which may be combined with one another unlessclearly exclusive: the lens of the autofocus imager is a poweradjustable lens, and the control device is operable to adjust the focallength of the lens; the lens of the autofocus imager is a positionadjustable lens, and the control device is operable to adjust theposition of the lens; calculating the length of the sample arm, usingthe absolute distance between the OCT source and the sample, andgenerating and transmitting the control signal is in real time;determining an absolute distance between the OCT source and the sampleis by reference to lens-distance reference data; and wherein thelens-distance reference data includes data corresponding to the distancebetween the OCT source and the sample at different focal lengths orpositions of the autofocus imager lens.

The above systems may be used with the above methods and vice versa. Inaddition, any system described herein may be used with any methoddescribed herein and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, whichare not drawn to scale, and in which:

FIG. 1 is a schematic representation of an OCT system;

FIG. 2 a schematic representation of a visualization system thatincludes an OCT system and an autofocus imager with a power adjustablelens;

FIG. 3 is a schematic representation of a visualization system thatincludes an OCT system and an autofocus imager with a positionadjustable lens; and

FIG. 4 is a flowchart of a method for optimizing OCT.

DETAILED DESCRIPTION

In the following description, details are set forth by way of example tofacilitate discussion of the disclosed subject matter. It should beapparent to a person of ordinary skill in the field, however, that thedisclosed embodiments are exemplary and not exhaustive of all possibleembodiments.

When performing OCT, it is important to obtain an analyzableinterference pattern to allow for proper measurements and imaging ofinternal target structures the sample beam passed through. To obtainsuch an interference pattern, it is important to minimize any differencebetween the length of the reference arm and the length of the samplearm. Preferably, any such difference in length is insubstantial and anyvariance is known. For example, the difference between the length of thereference arm and the length of the sample arm may be consideredinsubstantial when it is less than 100 mm. In an OCT system, the lengthof the reference arm refers to the distance between the OCT beamsplitter and the reference mirror. The length of the sample arm refersto the distance between the OCT beam splitter and the sample. Atpresent, adjustments to the length of the reference arm or sample armare performed manually.

In typical use of an OCT system, a user may manually adjust the positionof the OCT source back and forth until the length of the reference armand the sample arm are the same, and an optimal image is obtained.However, in certain instances, it may not be possible or practicable tomove the OCT source back and forth to get an optimal image, for example,when an OCT system is connected to a surgical microscope. In suchinstances, a user may be more concerned with getting a clear surgicalmicroscope view during surgery than obtaining an optimized OCT image. Inorder to obtain a clear surgical microscope view, the user may adjustthe focus of the surgical microscope or move the surgical microscope upor down, which alters the position of the OCT source and as a result,the length of the sample arm. To maintain an optimized OCT image, thelength of the reference arm must be adjusted as the focus or position ofthe surgical microscope is adjusted.

The disclosure provides a visualization system that incorporates anautofocus imager, which may generate data relating to a position or afocal length of the autofocus imager lens. The autofocus imager lens maybe, for example, a power adjustable lens in which the focal length ofthe lens may be adjusted, or a position adjustable lens in which theposition of the lens may be adjusted. By implementing an autofocusimager, the visualization systems herein provide automated adjustment ofthe length of the reference arm or the focus of the sample arm, ascompared to manual adjustment by a user.

A processor of the visualization system determines the distance betweenthe dichroic mirror and the sample using the data relating to theposition or the focal length of the autofocus imager lens. The processordetermines the absolute distance between the OCT source and the sampleusing the distance between the dichroic mirror and the sample. Theprocessor further determines the length of the sample arm using theabsolute distance between the OCT source and the sample. By making thesedeterminations, the visualization system can optimize OCT scanning, byadjusting the length of the reference arm, the focus of the sample arm,or both. The length of the reference arm may be adjusted, for example,via a control device connected to the reference mirror. The focus of thesample arm may be adjusted by either adjusting a position of an OCTlens, of the OCT system, or the focus of the OCT lens. The OCT lens,though not included in FIG. 1, may be at any position between the beamsplitter and the sample, which as shown, is any position on path 130 or150, as described further below in reference to FIG. 1. By adjusting thelength of the reference arm, the focus of the sample arm, or both, thevisualization systems perform optimized OCT scanning, which results inan interference pattern that is more analyzable, and accordingly, anoptimized OCT image.

Referring now to the drawings, FIG. 1 is a schematic representation ofan OCT system 100, which, as shown, includes a scanning mirror 105. OCTsystem 100 is connected to a processor 170, which is connected to memory155. OCT system 100 includes OCT beam splitter 102, detector 107,reference mirror 104, and OCT source 101. OCT source 101 generates anOCT source beam, which is propagated on path 110 toward OCT beamsplitter 102. OCT beam splitter 102 splits the OCT source beampropagated on path 110 into two component beams: (1) a sample beam thatis propagated along a sample arm, path 130, to a sample 106, after beingreflected off scanning mirror 105; and (2) a reference beam that ispropagated along a reference arm, path 120, to reference mirror 104.Sample 106 may be, for example, a patient's eye.

Once the sample beam reaches sample 106, it is reflected back toward OCTbeam splitter 102 on path 150. OCT beam splitter 102 combines thereflected sample beam, on path 140, and the reflected reference beam, onpath 150, to create an interference pattern. The combined reflectedbeams are called a “reflected OCT beam.”

The reflected OCT beam is directed to detector 107. Detector 107 may be,for example, a photodetector. Detector 107 detects the interferencepattern of the reflected OCT beam and generates data relating to theinterference pattern. Processor 170 receives the data from detector 107and may process the data to generate an OCT image of internal targetstructures that the sample beam passed through.

A processor 170 may include, for example a microprocessor,microcontroller, digital signal processor (DSP), application specificintegrated circuit (ASIC), or any other digital or analog circuitryconfigured to interpret and/or execute program instructions and/orprocess data. In some embodiments, processor 170 may interpret and/orexecute program instructions and/or process data stored in memory 175.Memory 175 may be configured in part or whole as application memory,system memory, or both. Memory 175 may include any system, device, orapparatus configured to hold and/or house one or more memory modules.Each memory module may include any system, device or apparatusconfigured to retain program instructions and/or data for a period oftime (e.g., computer-readable media). The various servers, electronicdevices, or other machines described may contain one or more similarsuch processors or memories for storing and executing programinstructions for carrying out the functionality of the associatedmachine.

FIG. 2 is a schematic representation of a visualization system 200 thatincludes an autofocus imager 203 with a power adjustable lens 207. Poweradjustable lens 207 may be incorporated into autofocus imager 203 orconnected to it. Power adjustable lens 207 is connected to a controldevice 290, which can adjust at least the focal length of the poweradjustable lens. Adjusting the focal length of power adjustable lens 207may be referred to as adjusting the “power” of the power adjustablelens. Visualization system 200 also includes surgical microscope 202with a surgical microscope eyepiece 260, processor 250, memory 251,dichroic mirror 204, visualization beam splitter 206, and OCT system280. OCT system 280 includes an OCT source 201, an OCT beam splitter, areference mirror, a detector, and an OCT lens.

Visualization system 200 optimizes the resulting interference pattern,and accordingly, the resulting OCT image, by performing optimized OCTscanning. To perform optimized OCT scanning, visualization system 200may adjust the length of the reference arm or the focus of the samplearm, of the OCT system. As discussed for FIG. 2, the reference arm andthe sample arm relate to the OCT system 280, not visualization system200. The focus of the sample arm may be adjusted by either adjusting aposition of the OCT lens, or the focus of the OCT lens. As describedabove, although not shown in FIG. 2, the OCT lens may be at any positionbetween the OCT beam splitter, of OCT system 280, and sample 205.

OCT source 201 generates an OCT source beam, which is propagated on path210 toward dichroic mirror 204. Dichroic mirror 204 may be incorporatedinto surgical microscope 202. Dichroic mirror 204 directs the OCT sourcebeam toward sample 205, along path 220. Sample 205 may be a patient'seye. Once the OCT source beam on paths 210 and 220 reaches sample 205,it is reflected back toward dichroic mirror 204 and directed back to OCTsystem 280, on path 230.

Dichroic mirror 204 is a mirror that has significantly differentreflection or transmission properties at two different wavelengths. Suchproperties allow the dichroic mirror to reflect the OCT source beam,which is generally near the infrared range and generally higher than a700 nm wavelength. In contrast, such properties also allow the dichroicmirror to transmit non-OCT light, which is in the visible range andgenerally less than a 700 nm wavelength. For example, non-OCT light maybe ambient light or light generated by the surgical microscope.

While the OCT source beam is being directed along paths 210 and 220,autofocus imager 203 receives non-OCT light reflected by the sample thathas passed through the dichroic mirror and has been directed by thevisualization beam splitter to the autofocus imager. Autofocus imager203 receives this non-OCT light through its power adjustable lens 207.Autofocus imager 203 can detect and generate data relating to the focallength and the position of power adjustable lens 207. The non-OCT light,on path 240, may be for example, ambient light or light generated by thesurgical microscope. On path 240, the transmitted non-OCT light passesthrough dichroic mirror 204 and is split into two component beams atvisualization beam splitter 206.

Visualization beam splitter 206 is a part of the surgical microscope202. Visualization beam splitter 206 splits the beam of non-OCT light,and directs one component beam to the autofocus imager lens 207 and theother component beam to the eyepiece of the surgical microscope 260 sothat the user can observe the sample 205.

Once autofocus imager 203 receives the autofocus beam, it can optimizethe focus of power adjustable lens 207 on the sample by adjusting atleast the focus of power adjustable lens 207. Autofocus imager 203 mayuse the non-OCT light to optimize the focus of the autofocus imager onthe sample by adjusting power adjustable lens 207. Autofocus imager 203can detect and generate data relating to the focal length or position ofpower adjustable lens 207.

Processor 250 can receive the data relating to the focal length andposition of power adjustable lens 207 and process it to determine thedistance between dichroic mirror 204 and the sample 205. Processor 250can determine the absolute distance between the OCT source and sample205, using the distance between the dichroic mirror and the sample.Processor 250 can further determine the length of the sample arm usingthe absolute distance between the OCT source and the sample.

Alternatively, processor 250 may determine the change in distancebetween dichroic mirror 204 and the sample 205 using the data relatingto the position or the focal length of the autofocus imager lens.Processor 250 may further determine the change in the length of thesample arm using the change in distance between the dichroic mirror andthe sample. In this example, processor 250 may still adjust thereference arm and focus of the sample arm to optimize the OCT system:(1) without determining or using the determination of the distancebetween the dichroic mirror and the sample; or (2) without determiningor using the determination of the absolute distance between the OCTsource and the sample. Instead, processor 250 may determine any changein distance between the dichroic mirror and the sample, determine achange in the length of the sample arm, and use that determination tooptimize the OCT system.

Processor 250 may generate a control signal to optimize the OCT system280 by adjusting the length of the reference arm or the focus of thesample arm, and transmit the control signal to the OCT system 280. Thelength of the reference arm may be adjusted, for example, via a controldevice. The focus of the sample arm may be adjusted by either adjustingthe position of an OCT lens, of the OCT system, or the focus of the OCTlens. By adjusting the length of the reference arm or the focus of thesample arm, any difference between the lengths of the reference arm andthe sample arm may be minimized, and preferably insubstantial. Byminimizing any difference between the lengths of the reference arm andthe sample arm, the visualization system optimizes the resultinginterference pattern and accordingly, the resulting OCT image.

In the visualization system of FIG. 2, the length of the “sample arm” isthe distance from OCT source 201 to the sample 205, which equalsL1+L2+L3, where L1 is the distance between OCT source 201 and dichroicmirror 204, L2 is the distance between dichroic mirror 204 and the edgeof surgical microscope 202, and L3 is the distance between the edge ofsurgical microscope 202 and sample 205. L1 and L2 are fixed. The onlyvariable parameter in the calculation of the length of the sample arm isL3, the changing distance between surgical microscope 202 and sample205.

In FIG. 2, the length of the “object distance” is the distance from thepower adjustable lens 207 to the sample 205, which equals L4+L5+L6,where L4 is the distance between the power adjustable lens 207 andvisualization beam splitter 206, L5 is the distance betweenvisualization beam splitter 206 and the edge of surgical microscope 202,and L6 is the distance between the edge of surgical microscope 202 andthe sample 205. As shown, L3 and L6 are the same distance. The distancebetween power adjustable lens 207 and a sensor of the autofocus imager203 is shown as L7.

In visualization system 200,

$\frac{1}{f} = {\frac{1}{\left( {{L\; 4} + {L\; 5} + {L\; 6}} \right)} + \frac{1}{L\; 7}}$in which “f” represents the focal length of power adjustable lens 207.This equation may be solved for L6 as follows:

${L\; 6} = {\frac{{fL}\; 7}{{L\; 7} - f} - {L\; 4} - {L\; 5}}$

As stated above and shown in FIG. 2, L6=L3. As a result, the absolutedistance between OCT source 201 and the sample 205, designated L_(OCT),can be calculated as:

$L_{OCT} = {{{L\; 1} + {L\; 2} + {L\; 3}} = {{L\; 1} + {L\; 2} + \frac{{fL}\; 7}{{L\; 7} - f} - {L\; 4} - {L\; 5}}}$

Of the parameters in the above equation, L1, L2, L7, L4, and L5 areproperties of the visualization system, as configured. Focal length “f”may be displayed or determined by autofocus imager 203. From there,L_(OCT) may be determined by processor 250.

As described above, L_(OCT), the absolute distance between OCT source201 and the sample 205, is determined using the distance between thedichroic mirror and the sample, which is determined using the datarelating to the position or the focal length of the autofocus imagerlens. In this example, the autofocus imager lens is power adjustablelens 207. Processor 250 determines a length of the sample arm using theabsolute distance between the OCT source and the sample, and generates acontrol signal to adjust either the position of an OCT lens or the focusof the OCT lens to minimize any difference between the lengths of thereference arm and the sample arm, which optimizes OCT scanning.

FIG. 3 is a schematic representation of a visualization system 300 thatincludes an autofocus imager 203 with a position adjustable lens 307, incontrast to the power adjustable lens 207 of visualization system 200.Autofocus imager 203 may optimize its focus on the sample by adjusting aposition of position adjustable lens 307. Position adjustable lens 307may be incorporated into autofocus imager 203 or connected to it.Position adjustable lens 307 is connected to a control device 290, whichcan adjust at least the position of the position adjustable lens.Visualization system 200 also includes surgical microscope 202 with asurgical microscope eyepiece 260, processor 250, memory 251, dichroicmirror 204, visualization beam splitter 206, and OCT system 280. OCTsystem 280 includes an OCT source 201, an OCT beam splitter, a referencemirror, a detector, and an OCT lens.

Visualization system 200 optimizes the resulting interference pattern,and accordingly, the resulting OCT image, by performing optimized OCTscanning. To perform optimized OCT scanning, visualization system 200may adjust the length of the reference arm or the focus of the samplearm, of the OCT system. As discussed for FIG. 2, the reference arm andthe sample arm relate to the OCT system 280, not visualization system200. The focus of the sample arm may be adjusted by either adjusting aposition of the OCT lens, or the focus of the OCT lens. As describedabove, although not shown in FIG. 2, the OCT lens may be at any positionbetween the OCT beam splitter, of OCT system 280, and sample 205.

OCT source 201 generates an OCT source beam, which is propagated on path210 toward dichroic mirror 204. Dichroic mirror 204 may be incorporatedinto surgical microscope 202. Dichroic mirror 204 directs the OCT sourcebeam toward sample 205, along path 220. Sample 205 may be a patient'seye. Once the OCT source beam on paths 210 and 220 reaches sample 205,it is reflected back toward dichroic mirror 204 and directed back to OCTsystem 280, on path 230.

While the OCT source beam is being directed along paths 210 and 220,autofocus imager 203 receives non-OCT light reflected by the sample thathas passed through the dichroic mirror and has been directed by thevisualization beam splitter to the autofocus imager. In contrast tovisualization system 200 of FIG. 2, in visualization system 300 of FIG.3, autofocus imager 203 receives this non-OCT light through its poweradjustable lens 207. Autofocus imager 203 can detect and generate datarelating to the focal length and the position of power adjustable lens207. The non-OCT light, on path 240, may be for example, ambient lightor light generated by the surgical microscope. On path 240, thetransmitted non-OCT light passes through dichroic mirror 204 and issplit into two component beams at visualization beam splitter 206.

Visualization beam splitter 206 is a part of the surgical microscope202. Visualization beam splitter 206 splits the beam of non-OCT light,and directs one component beam to the autofocus imager lens 307 and theother component beam to eyepiece of the surgical microscope 260 so thatthe user can observe the sample 205.

Once autofocus imager 203 receives the autofocus beam, it can optimizethe focus of position adjustable lens 307 on the sample by adjusting atleast the position of position adjustable lens 307. Autofocus imager 203may use the non-OCT light to optimize the focus of the autofocus imageron the sample by adjusting position adjustable lens 307. Autofocusimager 203 can detect and generate data relating to the focal length orposition of position adjustable lens 307.

Processor 250 can receive the data relating to the focal length andposition of position adjustable lens 307 and process it to determine thedistance between dichroic mirror 204 and the sample 205. Processor 250can determine the absolute distance between the OCT source and sample205, using the distance between the dichroic mirror and the sample.Processor 250 can further determine the length of the sample arm usingthe absolute distance between the OCT source and the sample.

Alternatively, processor 250 may determine the change in distancebetween dichroic mirror 204 and the sample 205 using the data relatingto the position or the focal length of the autofocus imager lens.Processor 250 may further determine the change in the length of thesample arm using the change in distance between the dichroic mirror andthe sample. In this example, processor 250 may still adjust thereference arm and focus of the sample arm to optimize the OCT system:(1) without determining or using the determination of the distancebetween the dichroic mirror and the sample; or (2) without determiningor using the determination of the absolute distance between the OCTsource and the sample. Instead, processor 250 may determine any changein distance between the dichroic mirror and the sample, determine achange in the length of the sample arm, and use that determination tooptimize the OCT system.

Processor 250 may generate a control signal to optimize the OCT system280 by adjusting the length of the reference arm or the focus of thesample arm, and transmit the control signal to OCT system 280. Thelength of the reference arm may be adjusted, for example, via a controldevice. The focus of the sample arm may be adjusted by either adjustingthe position of an OCT lens, of the OCT system, or the focus of the OCTlens. By adjusting the length of the reference arm or the focus of thesample arm, any difference between the lengths of the reference arm andthe sample arm may be minimized, and preferably insubstantial. Byminimizing any difference between the lengths of the reference arm andthe sample arm, the visualization system optimizes the resultinginterference pattern and accordingly, the resulting OCT image.

In the visualization system of FIG. 3, the length of the “sample arm” isthe distance from OCT source 201 to the sample 205, which equalsL1+L2+L3, where L1 is the distance between OCT source 201 and dichroicmirror 204, L2 is the distance between dichroic mirror 204 and the edgeof surgical microscope 202, and L3 is the distance between the edge ofsurgical microscope 202 and sample 205. L1 and L2 are fixed. The onlyvariable parameter in the calculation of the length of the sample arm isL3, the changing distance between surgical microscope 202 and sample205.

In FIG. 3, the length of the “object distance” is the distance from theposition adjustable lens 307 to the sample 205, which equals L4+L5+L6,where L4 is the distance between the position adjustable lens 307 andvisualization beam splitter 206, L5 is the distance betweenvisualization beam splitter 206 and the edge of surgical microscope 202,and L6 is the distance between the edge of surgical microscope 202 andthe sample 205. As shown, L3 and L6 are the same distance. In contrastto visualization system 200 of FIG. 2, the distance between positionadjustable lens 307 and a sensor of the autofocus imager 203 is shown asL7.

In visualization system 300,

$\frac{1}{f} = {\frac{1}{\left( {{L\; 4} + {L\; 5} + {L\; 6} + {\Delta\; d}} \right)} + \frac{1}{{L\; 7} - {\Delta\; d}}}$in which “f” represents the focal length of position adjustable lens307. This equation may be solved for L6 as follows:

${L\; 6} = {\frac{f\left( {{L\; 7} - {\Delta\; d}} \right)}{{L\; 7} - {\Delta\; d} - f} - {L\; 4} - {L\; 5} - {\Delta\; d}}$

As stated above and shown in FIG. 2, L6=L3. As a result, the absolutedistance between OCT source 201 and the sample 205, designated L_(OCT),can be calculated as:

$L_{OCT} = {{{L\; 1} + {L\; 2} + {L\; 3}} = {{L\; 1} + {L\; 2} + \frac{f\left( {{L\; 7} - {\Delta\; d}} \right)}{{L\; 7} - {\Delta\; d} - f} - {L\; 4} - {L\; 5} - {\Delta\; d}}}$

Of the parameters in the above equation, L1, L2, L7, L4, and L5 areproperties of the visualization system, as configured. Focal length “f”is fixed in this situation because position adjustable lens 307 isimplemented, as opposed to power adjustable lens 207, and Δd can be readfrom the display on autofocus imager 203. From there, L_(OCT) may bedetermined by processor 250.

As described above, L_(OCT), the absolute distance between OCT source201 and the sample 205, is determined using the distance between thedichroic mirror and the sample, which is determined using the datarelating to the position or the focal length of the autofocus imagerlens. In this example, the autofocus imager lens is position adjustablelens 307. Processor 250 determines a length of the sample arm using theabsolute distance between the OCT source and the sample, and generates acontrol signal to adjust either the position of an OCT lens or the focusof the OCT lens to minimize any difference between the lengths of thereference arm and the sample arm, of the OCT system, which optimizes OCTscanning.

Visualization system 200 of FIG. 2 or any component thereof may be usedwith visualization system 300 of FIG. 3 or any component thereof, andvice versa.

For both visualization systems 200 and 300, calculating the length ofthe sample arm, using the absolute distance between the OCT source andthe sample, and generating and transmitting the control signal may beperformed in real time. Real time may mean in less than half a second,in less than one second, or otherwise in less than the normal reactiontime of a user of the visual information. Also, determining L_(OCT), theabsolute distance between the OCT source and the sample, may beperformed by reference to lens-distance reference data. Thelens-distance reference data may include data corresponding to thedistance between the OCT source and the sample at different focallengths or positions of the autofocus imager lens.

FIG. 4 is a flowchart of a method for optimizing OCT. At step 405non-OCT light, reflected by a sample, is received at an autofocusimager. The sample may be, for example, a patient's eye. Non-OCT lightmay be, for example, ambient light or light generated by the surgicalmicroscope. At step 410, the focus of the autofocus imager on the sampleis optimized, using the non-OCT light reflected from the sample.

At step 415, data is generated, at the autofocus imager, relating to theposition or the focal length of an autofocus imager lens. The datagenerated may include any change in position or focal length of theautofocus imager lens, the change caused when the focus of the autofocusimager on the sample is optimized, using the non-OCT light reflectedfrom the sample. The autofocus imager lens may be, for example, aposition adjustable lens (as described in FIG. 3) or a power adjustablelens (as described in FIG. 2). The data generated may include only theposition of the autofocus imager lens, if a position adjustable lens isimplemented and only the position of the position adjustable lens isadjusted. In contrast, if a power adjustable lens is implemented, thedata received should include the focal length and the position of thepower adjustable lens.

At step 420, the distance between the dichroic mirror and the sample maybe determined based on the data relating to the position or the focallength of the autofocus imager lens. At step 425, L_(OCT), the absolutedistance between the OCT source and the sample, may be determined asdescribed in FIG. 2 for a visualization system with a power adjustablelens or as described in FIG. 3 for a visualization system with aposition adjustable lens. At step 430, the length of the sample arm, ofthe OCT system, may be determined, based on the absolute distancebetween the OCT source and the sample.

Alternatively to steps 420, 425, and 430, the change in distance betweenthe dichroic mirror and the sample may be determined, using the datarelating to the position or the focal length of the autofocus imagerlens, and the change in the length of the sample arm may be determined,using the change in distance between the dichroic mirror and the sample.In this example, the OCT system may still be optimized by adjusting thereference arm or focus of the sample arm: (1) without determining orusing the determination of the distance between the dichroic mirror andthe sample; or (2) without determining or using the determination of theabsolute distance between the OCT source and the sample. Instead, anychange in distance between the dichroic mirror and the sample isdetermined, and any change in the length of the sample arm is determinedand used to optimize the OCT system.

At step 440, a control signal may be generated to optimize the OCTsystem by adjusting the length of the reference arm, the focus of thesample arm, or both. The length of the reference arm may be adjusted,for example, via a control device connected to the reference mirror ofthe OCT system. The focus of the sample arm may be adjusted by eitheradjusting a position of an OCT lens, of the OCT system, or the focus ofthe OCT lens.

At step 450, the control signal may be transmitted to the OCT system toadjust either the length of the reference arm, the focus of the samplearm, or both. By performing such adjustments, the OCT performance isoptimized because any difference between the length of the reference armand the length of the sample arm is minimized. Preferably, any suchdifference in length is made insubstantial and any variance is known.For example, the difference between the length of the reference arm andthe length of the sample arm may be considered insubstantial when it isless than 100 mm. This results in an interference pattern that is moreanalyzable, and accordingly, an optimized OCT image.

Method 400 may be implemented using the visualization systems of FIG. 2or FIG. 3, or any other suitable system. The preferred initializationpoint for such methods and the order of their steps may depend on theimplementation chosen. In some embodiments, some steps may be optionallyomitted, repeated, or combined. In some embodiments, some steps of suchmethods may be executed in parallel with other steps. In certainembodiments, the methods may be implemented partially or fully insoftware embodied in computer-readable media.

For the purposes of this disclosure, computer-readable media may includeany instrumentality or aggregation of instrumentalities that may retaindata and/or instructions for a period of time. Computer-readable mediamay include, without limitation, storage media such as a direct accessstorage device (e.g., a hard disk drive or floppy disk), a sequentialaccess storage device (e.g., a tape disk drive), compact disk, CD-ROM,DVD, random access memory (RAM), read-only memory (ROM), electricallyerasable programmable read-only memory (EEPROM), and/or flash memory; aswell as communications media such wires, optical fibers, and otherelectromagnetic and/or optical carriers; and/or any combination of theforegoing.

The above disclosed subject matter is to be considered illustrative, andnot restrictive, and the appended claims are intended to cover all suchmodifications, enhancements, and other embodiments which fall within thetrue spirit and scope of the present disclosure. Thus, to the maximumextent allowed by law, the scope of the present disclosure is to bedetermined by the broadest permissible interpretation of the followingclaims and their equivalents, and shall not be restricted or limited bythe foregoing detailed description.

The invention claimed is:
 1. A visualization system comprising: an OCTsystem comprising an OCT source operable to generate an OCT source beam;an OCT beam splitter operable to split the OCT source beam into a samplebeam that travels along a sample arm until it is reflected by a sampleto form a reflected sample beam, and a reference beam that travels alonga reference arm until it is reflected by a reference mirror in the OCTsystem to form a reflected reference beam, and operable to combine thereflected sample beam and the reflected reference beam to form areflected OCT beam; and an OCT detector operable to receive thereflected OCT beam and operable to detect an interference pattern of thereflected OCT beam; a surgical microscope; a dichroic mirror operable toallow non-OCT light to substantially pass through and operable toreflect the sample beam; and a visualization beam splitter operable todirect non-OCT light into both the surgical microscope and; an autofocusimager, the autofocus imager operable to: receive non-OCT lightreflected by the sample that has passed through the dichroic mirror andan autofocus imager lens, and generate data relating to a position and afocal length of the autofocus imager lens; and a processor operable to:determine a distance between the dichroic mirror and the sample usingthe data relating to the position and the focal length of the autofocusimager lens; determine an absolute distance between the OCT source andthe sample using the distance between the dichroic mirror and thesample; determine a length of the sample arm using the absolute distancebetween the OCT source and the sample; generate a control signaloperable to optimize the OCT system by adjusting the length of thereference arm or the focus of the sample arm; and transmit the controlsignal to the OCT system.
 2. The visualization system of claim 1,wherein the autofocus imager lens is a power adjustable lens, andwherein a focal length of the power adjustable lens is adjusted.
 3. Thevisualization system of claim 1, wherein the autofocus imager lens is aposition adjustable lens, and wherein a position of the positionadjustable lens is adjusted.
 4. The visualization system of claim 1,wherein the processor is operable to: calculate the length of the samplearm, using the absolute distance between the OCT source and the sample;and generate and transmit the control signal in real time.
 5. Thevisualization system of claim 1, wherein the processor is operable todetermine the absolute distance between the OCT source and the sample byreference to lens-distance reference data.
 6. The visualization systemof claim 5, wherein the lens-distance reference data includes datacorresponding to the distance between the OCT source and the sample atdifferent focal lengths or positions of the autofocus imager lens. 7.The visualization system of claim 1 wherein the autofocus imager lens isselected from the group consisting of: a power adjustable lens and aposition adjustable lens.